In audio compression, audio signals are divided into blocks, each block composed of a prescribed number of data samples (hereinafter referred to as “audio samples”), and for each block the audio signals are converted to frequency signals that represent prescribed encoded frequency components, and audio compression data is generated. In encoding processing based on AAC (Advanced Audio Coding), in order to produce smooth audio compression data, the processing in which adjacent blocks are partially overlapped (hereinafter referred to as “overlap transform”) is performed (see Non-Patent Reference 1, for example).
Further, audio streams composed of audio compression data require rate controls such as CBR (Constant Bit-Rate) and ABR (Average Bit-Rate) in order to satisfy buffer management constraints
(see Non-Patent References 1 and 2, for example).
In audio editing, the editing of audio streams composed of audio compression data is frequently performed, and in some cases, such audio streams must be stitched together. Because audio compression data is generated by the partial overlap transform of blocks consisting of a prescribed number of audio samples, a simple joining of different audio streams produces frames in which data is incompletely decoded at joints of audio stream data, resulting in artifacts (distortions) in some cases. Further, simplistic joining of audio compression data can violate buffer management constraints, potentially resulting in buffer overflow or underflow. To prevent these issues, when joining different audio streams it was previously necessary to decode all audio streams and re-encode them.
On the other hand, there is an MPEG data storage method wherein image data encoded using the MPEG (Moving Picture Experts Group) coding method (hereinafter referred to as “MPEG image data”) is re-encoded by limiting two identical sets of MPEG data to the joint of MPEG image data and the MPEG data is recorded in a storage medium (see Patent Reference 1). When joining two sets of different MPEG image data, this technique stores in memory information on the amount of space required in the VBV (Video Buffer Verifier) buffer in a prescribed segment and controls the VBV buffer based on this information to prevent a buffer overflow or underflow.